1. Field of the Invention
This invention relates generally to a zipper, and more particularly, but not by way of limitation, to a progressive compressive zipper for use in joining two halves of a training bag.
2. Description of the Related Art
Free standing punching or training bags are typically constructed with blow molded or injection molded plastic bases, which are weighted with up to 300 lbs. of weighted material such as sand, water, or other material. The base is fitted with a separate vinyl punching bag, which is mounted after loading the base with the weighted material. The problem is that it is difficult to assemble and/or connect a heavy weighted plastic base with a vinyl-skinned soft punching bag top such that the device remains easy to assemble while providing the structure and durable functional properties required of a punching bag.
It is desirable to provide a punching bag with the base and top made of like material, such as vinyl. Such a punching bag is similarly difficult to assemble and/or connect because the foam-filled top must be forcefully compressed and joined to the base to produce a firm connection such that the vinyl top skin is stretched firmly over the foam with no wrinkles and firmly to the base so that the rebounding properties of the foam are consistent when struck by the user.
Zippers are commonly used to connect two items or two parts of the same item together. No other zipper closure device, however, utilizes a zipper construction to connect two independent components while using leverage by the closure to compress the two parts together. While expandable suitcases utilize zippers to expand/contract the relative material capacity of luggage storage space, luggage zippers of this design are permanently attached to one piece of material. Such luggage zippers do not connect two separate pieces, they remain permanently connected, and they do not enable connecting two dissimilar components. Furthermore, such luggage zippers do not compress one component to another, but merely alter the capacity of the luggage.
Based on the foregoing, it is desirable to provide a zipper for connecting the top and base of a training bag.
It is further desirable for the zipper to be constructed to act as a ramp to gradually compress the top to the base.
It is further desirable for the zipper ramp incline to maintain an optimum balance between the coefficient of friction between joining zippers and the forces required to fully compress the foam firmly to the base.
It is further desirable for the ramp-up zipping method to allow one person to easily and effectively attach the top to the weighted base.